1. Field of Invention
The present invention relates generally to compositions and methods of preparing compositions for coloring cementitious materials. More particularly, it relates to compositions and methods for preparing compositions using efflorescence control agents, particulated polymers, and a colorant for coloring cementitious materials.
2. Description of Related Art
Concrete is a mixture of fine and coarse aggregates firmly bound into a monolithic mass by a cementing agent. The cement generally used in forming concrete is Portland cement, although other inorganic hydraulic cements are available, which, upon hydration, form relatively insoluble bonded aggregations of considerable strength and dimensional stability. Portland cement consists mainly of tricalcium silicate and dicalcium silicate. The strength of the cementing agent is a function of the water-cement ratio, and therefore strength will vary widely depending upon the amount of water used. To obtain maximum strength, the water-cement ratio should be kept as low as possible. The aggregates are typically sand and crushed stone or gravel, although crushed clay or cinders can also be used in forming concrete. The formation of concrete is a process by which the voids between the particles of the coarse aggregate are filled by the fine aggregate, and the whole is cemented together by the binding action of the cement.
Concrete is an important building material extensively employed in modern construction because of its strength, permanency, and relatively low cost. The long-term success of concrete in meeting any particular set of conditions depends upon the proper correlation of many factors bearing on the selection and mixing of the materials, the placing of the concrete, and the original design.
Research and development in the science of concrete proportioning has advanced significantly in determining the best and most economical mix for a given condition, i.e., where the concrete may be subject to problems, for example, weathering, vibration, freezing, thawing, and other conditions in any selected environment.
One of the problems associated with concrete is efflorescence. Efflorescence is the deposition of calcium carbonate on the surface of masonry units. Deposition takes place as calcium ions in the cement migrate to the surface of a unit and react with atmospheric carbon dioxide, thereby forming calcium carbonate. The appearance and function of a masonry unit which has effloresced is compromised by the reaction. In preventing the reaction, and therefore maintaining the integrity and aesthetic appearance, chemical admixtures are employed in the formulation.
Stearate-containing compounds are used to prevent efflorescence. These stearate compounds are known in the art as efflorescence control agents (ECAs). Although stearate-containing compounds minimize or eliminate efflorescence, they are also known to adversely affect the durability of concrete. Concrete durability is a function of the totality of the polymerization of the cementitious materials in a mix. Because ECAs hinder polymerization, use of ECAs yield a weaker polymer structure and hence a less durable concrete. Typical ECAs include calcium stearate, zinc stearate, aluminum stearate, among other suitable compounds of stearic acid, salts and derivatives thereof, and mixtures thereof.
Durability of concrete is enhanced by using monomers, polymers, copolymers, and emulsions. Emulsions are generally used for the synthesis of many vinyl and diene polymers and for copolymerization. The polymer produced is in a latex of fine particles, or the latices are coagulated by the addition of chemicals to produce the polymer in a solid form. Typical polymers and copolymers employed include styrene butadiene, polyvinyl acetate, acrylonitrile-butadiene rubber, polyacrylic esters, polyvinylvinylidene, polyvinylidene ester, vinyl chloride, polyethylene-vinyl acetate, polyepoxide, polyurethane, acrylic latex, and mixtures thereof. An example of the use of polymers in concrete is found in U.S. Pat. No. 3,650,784 to Albert which describes a method for improving concrete properties by adding various polymers to fill the pore structure inherent in concrete.
ECAs used in combination with polymers lead to superior concrete properties as described in U.S. Pat. No. 5,922,124 to Supplee, assigned to RandM Chemical Technologies, Inc., the disclosure of which is hereby incorporated by reference as if set forth at length. Improved heat and freeze-thaw durability resulting from reduced efflorescence and stability against ultraviolet light exposure are exemplified in the patent.
The coloring of concrete and other building materials is known. Common concrete colorants are those specified in ASTM C979-86, Standard Specification for Integrally Colored Concrete. The ASTM standards cover the basic requirement for colored and white pigments in powder form to be used as admixtures in concrete for producing integrally colored concrete. The colorants listed in the ASTM specification are generally inorganic pigments which withstand various physical and chemical effects of the intended end use.
The pigments are tested for various properties, including light fastness or resistance to light, alkali resistance, water wettability, atmospheric curing stability, water solubility, and the total sulfates. Inorganic mineral oxides and one specific type of carbon black pigment meet these criteria. Typical pigment types manufactured for coloring concrete include, as set forth in the ASTM standards, synthetic iron oxides, yellows, reds, browns, and black; natural brown iron oxides, chromium oxide green, cobalt blue, and concrete grade carbon black.
U.S. Pat. No. 5,395,442 to Dunton describes a lightweight roof tile with high polymer content, for example, acrylic latex, for adding strength, i.e., durability, with minimally increasing the weight. Organic pigments and inorganic pigments may be used to produce a colored rooftile.
Other patents describe strengthening cementitious veneers, building faces, wall panels, refractory, roofing, and siding articles, and artificial rock by adding polymers. For example, U.S. Pat. No. 4,185,431 to Brownlee employs a polymer emulsion as a wetting agent that is mixed with cement, aggregate, and dry paint pigments for a facing composition. U.S. Pat. No. 4,152,168 to Yano describes a process in which an aqueous colored cement composition containing inorganic particles is applied to the surface of an uncured cement product. U.S. Pat. No. 4,420,525 to Parks describes thin, decorative colored cementitious veneers for walls, floors, and ceilings, and a method of making the veneers. The pigments employed in the colored hydraulic cement mix are natural or inert colors or synthetic materials. Acrylic polymers are optionally included in the mix. U.S. Pat. No. 4,956,013 to Motoki describes a refractory coating composition that includes a hydraulic cement, a re-emulsion type powdery vinyl resin, aluminum hydroxide powder, a carbonate, and lightweight aggregate. In addition to the five components described, pigments as coloring agents may be contained in the composition. U.S. Pat. No. 4,644,719 to Salazar describes a decorative wall panel that includes a reinforced base layer and a patterned top layer composed of Portland cement, sand, and a pigmented binder. U.S. Pat. No. 5,248,338 to Price describes colored marbled concrete that is prepared with concrete, mortar or tile grout dye. U.S. Pat. No. 4,043,826 to Hum describes a process for making artificial rocks by molding a composition that includes cement, a lightweight filler, water, a curing agent for the cement and an acrylic resin latex, and thereafter nonuniformly coloring the hardened rock with cement dyes or pigments. The latex paint used in the artificial rock composition is based on acrylic resins, to which minor amounts of alkyd resins can be included. The colorant material utilized includes ultramarine blue, carbon black, lamp black, and red, yellow and brown oxides.
U.S. Pat. Nos. 5,558,708, 5,951,752, and 5,846,315 to Johansen, Jr. describe compositions for coloring cement-based compositions such as mortars and grouts. The composition includes a cement-based component and an aqueous pigment component. Additional components include suspension enhancing agents and latex polymer solids, among others. The multi-component coloring systems and methods are described in the patents as not requiring sophisticated measuring devices, as a predetermined amount of an aqueous pigment and a predetermined amount of a cement are provided. The cement component and the pigment component are mixed together to produce a final composition. A pigment component used in the system is described in U.S. Pat. No. 5,362,322.
U.S. Pat. No. 5,362,322 to Johansen uses pigmented resin systems for grouting of ceramic tiles, pavers, and quarry tiles. A first component comprises an epoxy resin and the second component comprises an epoxy hardener. One of the components includes a color pigment additive. Color pigments employed in the system include metal oxides, metal oxide silicates, napthols, chromium oxides, nickel antimony titanium, titanium dioxide, alumino silicate and carbon black. Sophisticated measuring devices are described as unnecessary in providing the multi-component colorant system.
There remains a need for a concrete admixture composition for enhancing the physical properties of concrete, i.e., minimizing efflorescence and increasing durability, which also enhances the durability and retention of a colorant, without requiring sophisticated measuring devices.
Briefly described, the invention comprises a composition for coloring concrete, including a hydrophobic efflorescence control agent selected from the group consisting of calcium stearates, zinc stearates, sodium stearates, butyl stearate, stearic acid derivatives, stearic acid salts, and a mixture thereof; a particulated polymer selected from the group consisting of styrene-based polymers and copolymers, acrylic-based polymers and copolymers, polyvinyl acetates, polyepoxides, polyurethanes, butadiene rubbers, and a mixture thereof, and a colorant, wherein the composition improves the durability of the concrete while enhancing the durability and retention of said colorant.
In an alternate embodiment, the invention comprises a concrete admixture composition, including about 0.1% by weight to about 85% by weight of a hydrophobic efflorescence control agent; about 0.5% by weight to about 75% by weight of a particulated polymer, said particulated polymer having particle sizes of about 50 angstroms to about 7,000 angstroms; and about 0.001% by weight to about 80% by weight of a colorant in an aqueous dispersion of the total weight of the composition.
The composition also includes a property enhancing additive selected from the group consisting of plasticizers, surfactants, rheology modifiers, biological control agents, and a mixture thereof.
The efflorescence control agent is selected from the group consisting of calcium stearates, zinc stearates, sodium stearates, butyl stearate, stearic acid derivatives, stearic acid salts, tall oil fatty acids, vegetable and animal fats, emulsions based on white grease, silicone compounds, siliconates, and siloxanes, waxes, wax emulsions, soaps and fatty acids, vegetable oils and emulsions, petroleum residues, including mineral oil, paraffin, and bitumens, various pozzolanics, including fly ash, blast furnace slag, diatomaceous earth, inert fillers, including talc, bentonite, and siliceous powders, and a mixture thereof. The particulated polymer is selected from the group consisting of styrene-based polymers and copolymers, acrylic-based polymers and copolymers, polyvinyl acetates, polyepoxides, polyurethanes, butadiene rubbers, and a mixture thereof. The colorant is selected from the group consisting of inorganic mineral oxides, carbon black pigment, organic pigments, high chroma metallic pigments, and a mixture thereof, and can be in dry pigment form, or in a predispersed form.
The method of manufacturing a concrete admixture formulation includes the steps of: formulating a first mixture by preparing a dispersion of a stearate-containing compound, said compound comprising about 0.1% by weight to about 85% by weight; mixing the first mixture until blended; formulating a second mixture by adding a particulated polymer and a plasticizer to the first mixture, said polymer comprising about 0.5% by weight to about 75% by weight, said polymer having particle sizes of about 50 angstroms to about 7,000 angstroms; mixing the second mixture until blended; stabilizing the second mixture with an effective amount of a rheology modifier and an effective amount of a biocide; adding a colorant and mixing until blended, said colorant comprising about 0.001% by weight to about 80% by weight of a colorant in an aqueous dispersion.
The various features and advantages of the present invention may be more readily understood by reference to the following detailed description.
The following detailed description is of the best presently contemplated mode of carrying out the invention. It is not intended in a limiting sense, and is made for the purpose of illustrating the principles of the invention.
Concrete chemical admixtures include any and all substances that are added to concrete batches that are not cement or mineral aggregates. Various chemical admixtures are added to concrete batches to enhance (or to prevent) physical and/or chemical properties and attributes of the mixture.
The present invention comprises a composition for coloring concrete, including a hydrophobic efflorescence control agent selected from the group consisting of calcium stearates, zinc stearates, sodium stearates, butyl stearate, stearic acid derivatives, stearic acid salts, and a mixture thereof, a particulated polymer selected from the group consisting of styrene-based polymers and copolymers, acrylic-based polymers and copolymers, polyvinyl acetates, polyepoxides, polyurethanes, butadiene rubbers, and a mixture thereof, and a colorant, wherein the composition improves the durability of the concrete while enhancing the durability and retention of said colorant.
In an alternate embodiment, the present invention includes a concrete admixture composition that comprises about 0.1% by weight to about 85% by weight of a hydrophobic efflorescence control agent, about 0.5% by weight to about 75% by weight of a particulated polymer, said particulated polymer having particle sizes of about 50 angstroms to about 7,000 angstroms; and about 0.001% by weight to about 80% by weight of a colorant in an aqueous dispersion. It is intended that the phase xe2x80x9cby weightxe2x80x9d indicates the weight of the total composition.
The efflorescence control agents most commonly used include stearate compounds. Although these compounds are known to be detrimental to the durability of concrete, they are employed to prevent the formation of calcium carbonate on the surface of the masonry unit which is detrimental to the function and adversely affects the appearance of concrete structure. Preferably, the amount of stearate compound used in the present invention comprises between about 0.1 to about 85% by weight. In a more preferred embodiment, the amount of stearate compound employed ranges between about 0.25 to about 70% by weight. In the most preferred embodiment, the amount of stearate compound added to the composition ranges between about 25% to about 45% by weight.
Preferred efflorescence control agents are calcium stearates, zinc stearates, stearic acid and salts thereof, butyl stearates, and sodium stearates. Other efflorescence control agents suitable for use in the present invention include tall oil fatty acids, vegetable and animal fats, emulsions based on white grease, silicone compounds, siliconates, and siloxanes, waxes, wax emulsions, soaps and fatty acids, vegetable oils and emulsions, petroleum residues, including mineral oil, paraffin, and bitumens, various pozzolanics, including fly ash, blast furnace slag, diatomaceous earth, inert fillers, including talc, bentonite, and siliceous powders. The above-noted ECAs are readily available from various vendors. For example, available products include Color Cure from RandM Chemical Technologies, Inc. of Washington, N.J.; Calsan from BASF of Charlotte, N.C., both calcium stearate dispersions. Other products available include butyl stearate from Acros Chemicals of Pittsburgh, Pa., butyl stearate from Witco Chemicals of Houston, Tex., and zinc stearate from Sigma-Aldrich, of St. Louis, Mo. Of these, Calsan from BASF or Color Cure from RandM Chemical Technologies is preferred.
The durability of concrete is the function of the totality of the polymerization of the cementitious materials in the mixture. As discussed above, ECAs hinder polymerization and therefore yield a weaker polymer structure with lower durability. There are, however, compounds that are known to increase durability. Organic polymers, copolymers, emulsions, and monomers increase durability to concrete structures. Preferred polymeric dispersions for use in the present invention include Color Cure XD and Color Cure XDL, a calcium-stearate/styrene acrylic dispersion, available from the RandM Chemical Technologies, Inc., UCAR 820, a latex emulsion, available from Union Carbide of Cary, N.C., and Kelsol 305, a modified polyester dispersion available from Reichhold Chemicals, of Research Triangle Park, N.C.
Polymers preferred for use in the invention also include Wallpol 40152-07, a vinyl acetate polymer, and Kelsol 4097, an acrylic modified polyester, both available from Reichhold Chemicals, Acronal 702 or BASF 400 resin, both styrene modified acrylics available from BASF. In a more preferred embodiment, the resin is styrene butadiene or styrene acrylic from BASF, Union Carbide, or Reichhold. In the most preferred embodiment, styrene acrylic resin from Union Carbide is employed.
The preferred addition rate for the polymeric fraction of the composition is between about 0.5 to about 75% by weight. In a more preferred embodiment, an amount between about 20% to about 70% by weight is used. In the most preferred embodiment, the amount used ranges between about 60% to about 70% by weight. The preferred particle size of the polymer ranges from about 50 angstroms to about 7,000 angstroms.
In combination, the ECA and the polymeric fraction of the composition perform the desired role and lead to superior concrete properties. The superior properties are measured against those units with one or the other component, as set forth in U.S. Pat. No. 5,922,124, assigned to RandM Chemical Technologies, Inc.
It has been discovered that the technology disclosed in U.S. Pat. No. 5,922,124 enhances, protects, and binds colorants into and or onto concrete and other cementitious substances. The scientific theory concerning this phenomenon, although not wishing to be limited thereby, has been developed in the paint and coating systems industry through many years of commercially successful products. The theory is that a monomer, polymer, copolymer, or emulsion form a barrier, film, or encapsulate pigment particles onto and or into a substrate. The protective shield formed of the polymer hinders the effects of atmospheric degradation, known as weathering. Unless pigment particles are protected by a protective shield, the pigments particles are adversely affected by degradation, and are washed-out, removed, or otherwise subjugated.
The preferred amount of colorant employed in one embodiment of the present invention is from about 0.001 to about 80% by weight, more preferred is from about 0.1 to about 25% by weight. In the most preferred embodiment, the colorant content is between about 0.5% to about 20% by weight. Of course, the amount of colorant added to the present composition depends on the color desired and/or the intended end use.
Common concrete colorants preferred for use in the present invention include the common, established, and acceptable colorants set forth in ASTM C979-86, Standard Specification for Integrally Colored Concrete. The common concrete colorants are inorganic mineral oxides, with the exception of one type of carbon black pigment. The acceptability of the pigments for use in concrete structures is based upon scientific evidence of the capability to withstand various physical conditions and chemical reactions. The properties considered include light fastness, alkali resistance, water wetability, atmospheric curing stability, water solubility, and total sulfates. Heretofore, only inorganic mineral oxides and one specific type of carbon black pigment meet these criteria for use in concrete, which herein are referred to as common pigments.
It has advantageously been found that, in addition to the common colorants discussed above, that organic pigments, including all common black pigments, and high chroma metallic pigments can be used in the present invention. These pigments are hereafter referred to as uncommon pigments, as they are not generally used in the concrete industry for coloring concrete for a variety of reasons.
Uncommon pigments useful in the present invention include Zulu Blues, Zulu Greens, Sunglow Yellows, and Citation Reds from Engelhard Corp. Also available from Engelhard Corp. are Aurasperse aqueous dispersions. Additionally, Fanchon yellows, Palomar Greens and Palomar Blues, Indofast violet are available from Bayer Corp. Day-Glo Color Corp. of Cleveland, Ohio, provides the following organic pigments: Aurora Pink, Arc Yellow and Saturn Yellow. A carbon black pigment, LB-1011, is available from Elementis Pigments Inc., of Fairview Heights, Ill. Other useful carbon black pigments include Carbocolor from Cancarb of Alberta, Canada; Hansa Yellows, Permanent Yellows, and Lithol Red from Kingland Chemical Co. of Hangzhou, China; and phthalocyanine blue, phthalocyanine green, Arylide yellows, Quinacridone Orange and Magenta from Sun Chemical Corp. of Fort Lee, N.J. Also available from Sun Chemical is Pigment Black #7.
In a preferred embodiment, the pigments for use in the present invention include Phthalocyanine greens and blues, carbon black dispersions, Arylide yellows and Lithol Reds. In the most preferred embodiment of the invention the following pre-dispersed pigments are used: Aurasperse dispersions from Engelhard and Sunsperse dispersions from Sun Chemical Corp.
When used with the present invention, these uncommon pigments are stabilized in the substrate, the weatherability of a concrete unit including the colorant is increased; the efflorescence is minimized, and the durability is increased. As set forth in the Examples following this description, the color shift is also minimized.
The preferred embodiments for manufacturing the invention are two-fold. One embodiment uses a dry pigment, whereas the other embodiment uses a pre-dispersed pigment. One preferred embodiment using a dry pigment requires additional manufacturing steps discussed below for dispersing the dry pigment into a fluid matrix.
Using the preferred pre-dispersed pigment, a suitable process for manufacturing a composition includes agitating a suspension of stearate salt, acid, or organo-functional form in a solvent, for example, water, to which a dispersant has already been added. After sufficient mixing, plasticizers and polymers are added and either ground or mixed with high-speed dispersion equipment. The dispersion is then stabilized with rheology modifiers and biocides. Into the dispersion a pre-dispersed pigment is added, mixed, and ground to expedite pigment/resin interaction and encapsulation. To avoid additional manufacturing steps involved with dry pigments, the most preferred embodiment uses pre-dispersed pigments.
Dry pigments suitable for use in the present invention can be used by adding a dry pigment to a high-speed disperser to which a dispersant has been added. A preferred dispersant is Curesperse RM, a polyacrylate dispersion, available from RandM Chemical Technologies, Inc. Wetting, grinding and deagglomeration are carried out in subsequent steps. The pigment dispersion is stabilized by the addition of thixotropes and biocides. Preferred thixotropes are cellulosic compounds and a preferred biocide is Proxel, (1,2-benzisothiazolin-3-one) from Avecia of Wilmington, Del. One or more thixotropes and biocides may be used in the present invention, depending upon the intended use of the concrete structure.
In addition to the foregoing, the following additives can be included in the composition: plasticizers, lubricants, dispersants, rheology modifiers, and biological control agents known to those with skill in the art as conventional additives to concrete.
While not wishing to be limited by any scientific theory, the present invention performs and functions synergistically in the particular combinations disclosed, and surprisingly stabilizes and makes useful heretofore unusable uncommon pigments in coloring concrete.
The present invention shall be described in further detail by reference to the following examples which are provided for illustrative purposes only, and are not intended to be limiting. Many modifications and variations are apparent to those skilled in the art, which do not depart from the scope of the claims. Comparative examples are also presented.